A common and well known form of harvesting machine is a rotary combine. Rotary combines are available in various designs and models to perform the basic functions of harvesting, threshing, and cleaning of grain and other crop materials.
A typical combine includes a crop harvesting apparatus which reaps planted grain stalks and then feeds the grain stalks to a separating or threshing apparatus. The grain stalks or other crop harvested in the field is rearwardly moved from the crop harvesting apparatus and introduced to a threshing assembly by a feeder mechanism.
In combines, the threshing assembly includes a generally tubular rotor casing mounted on a frame of a combine and a driven rotor disposed within the casing in co-axial relationship therewith. The rotor and casing have cooperating threshing instrumentalities arranged thereon for separating and threshing grain from material other than grain. In such a combine, which has been available for a number of years, the grain is threshed several times repeatedly, but gently, as it spirals around the rotor and passes through openings in the rotor casing.
The ability to transfer material from the feeder mechanism to the rotor assembly is a key factor in efficient and effective combine operation. To enhance the transfer of crop material, a forward end of the rotor casing of some axial-flow combines is configured with an outwardly flared funnel-like frusto-conical transition section. The transition section surrounds a vaned impeller arranged at a forward end of the rotor.
At the discharge end thereof, the feeder mechanism introduces a continuous mat of crop material, having a width approximately equal to the width of the open end of the transition section, to the rotor assembly. The vaned impeller receives material in an undershot manner from the feeder mechanism and moves the material radially outward toward the transition section. The inner surface of the transition section combines with the impeller in moving the crop material axially rearward toward the threshing instrumentalities on the rotor.
Since there is considerable backlash of material which is "chewed" from the mat of crop material issuing from the feeder mechanism, conventional rotary combines provide a planar end wall or door transversely extending across a forward end of the rotor casing to confine the crop material which is fed into the rotor casing. Residual crop material which is not moved axially rearward toward the threshing instrumentalities on the rotor tends to whirl about the face and periphery of the impeller and reduces combine efficiency. Besides tending to wrap about a forward bearing mount for the rotor assembly, such residual crop material tends to create a backfeed problem for the feeder mechanism. As will be appreciated, such problems hinder operativeness of the combine thereby reducing combine capacity.
Where a planar end wall is employed, it has been found that the backlash of crop material impacts against such wall and builds up thereon. Ultimately, this residual crop material forms a circular cake which clogs the impeller due to the upthrust of material on one side of the rotor casing and the downthrust of material on the other side thereof. Thus, a rotating circular disk of material is created within the rotor casing in advance of the impeller. As this disk becomes thicker, it eventually establishes a solid circular mat which can no longer rotate and, ultimately, causes the engine to stall. As will be appreciated, moist crop materials further aggravate the problem. To clean and clear this problem, of course, requires valuable time which is a premium during a harvesting operation.
Therefore, there is a need and a desire for a device which improves the rearward movement of crop material toward the threshing instrumentalities on the rotor in a manner reducing or avoiding backfeed to the feeder mechanism and prevents crop from wrapping about the front rotor bearing.